Liquid crystal display device

ABSTRACT

In a liquid crystal display device having a pixel substrate  1,  a opposite substrate  2  and a liquid crystal layer  3  disposed between the pixel substrate  1  and the opposite substrate  2,  the pixel substrate  1  has a transparent substrate  4,  a pixel electrode  5  provided on the transparent substrate  4,  an orientation control slope portion  6  which is provided on the pixel electrode  5,  sloped in different directions within each pixel and formed of organic film such as acrylic resin, and an orientation layer  7  coated on the orientation control slope portion  6,  and the opposite substrate  2  has a transparent substrate  8,  a opposite electrode  9  provided on the transparent substrate  8  and an orientation layer  10  coated on the opposite electrode  9.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of application Ser. No. 09/307,741,filed May 10, 1999 now U.S. Pat. No. 6,476,894, and related to aconcurrently filed application, entitled: Method of Manufacturing LiquidCrystal Display Device Ser. No. 10/255,647, and based on Japanese PatentApplication No. 10-129379, filed May 13, 1998, by Hironori KIKKAWA. Thisapplication claims only subject matter disclosed in the parentapplication and therefore presents no new matter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device and amanufacturing method therefor and particularly to a liquid crystaldisplay device having a wide range of viewing angle and a method ofmanufacturing the same.

2. Description of the Prior Art

In general, liquid crystal display devices have been used as displaydevices for various electronic equipment, etc. because they can bemanufactured to be thin in thickness and light in weight. However, theliquid crystal display device has a disadvantage that the viewing anglethereof is narrower than CRT. Therefore, a technique for widening theviewing angle of the liquid crystal display device has been hithertoproposed.

FIG. 10 is a perspective view showing a conventional liquid crystaldisplay device disclosed in Japanese Patent Laid-open Publication No.7-199193. In the conventional liquid crystal display device, unevensurface 52 is provided at each pixel 51 on one substrate 56 or bothsubstrates 56, 57. FIG. 10 shows a case where uneven surfaces 52 areprovided on the substrate 56. Upon applying a voltage between thesubstrates 56 and 57, the rise-up direction of liquid crystal molecules53 between the substrates 56 and 57 is determined by an angle which isdependent on the surface structure of the substrate 56, whereby areas 54and 55 having different orientation directions are provided at thevoltage application time and the visual characteristic is compensatedbetween the respective areas 54 and 55. Therefore, a liquid crystaldisplay device having a wide range of viewing angle can be obtained.

FIGS. 11A to 11D are cross-sectional views showing a series of steps ofa method of manufacturing a substrate used for the above conventionalliquid crystal display device.

First, thermoplastic resist 61 is coated on substrate 60 with electrodes(FIG. 11A).

Subsequently, the resist 61 is partially shielded and then exposed tolight to dissolve and remove undesired portions of the resist, wherebyresist 61 a remains in a partial area (FIG. 11B).

Subsequently, the substrate 60 is heated to deform the resist 61 a,thereby forming resist 61 b having an uneven structure surfacerespectively (FIG. 11C).

However, the conventional liquid crystal display device described abovehas a disadvantage that it has lower transparency as compared withsimilar organic materials having no photosensitive group because aphotosensitive resist is used even when the whole-surface light exposureis performed, so that a display image is darkened or colored.

Furthermore, it is described in the above publication that according tothe method of manufacturing the substrate used in the above conventionalliquid crystal display device, slant and uneven portions are formed in awide range by deforming the thermoplastic resist. However, thethermoplastic resist is actually deformed at only the end portions ofthe residual resist like the resist 61 c, and it is difficult to formthe slant and uneven portions in a wide range (FIG. 11D). Accordingly,the conventional liquid crystal display device has a disadvantage that aregulation force is insufficient to keep the uniform rise-up directionand thus a stable orientation state cannot be obtained.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a liquid crystaldisplay device having a wide range of viewing angle characteristic withwhich transparency is enhanced and a stable orientation state can beobtained, and a method of manufacturing the liquid crystal displaydevice.

In order to attain the above object, according to a first aspect of thepresent invention, a liquid crystal display device having a pair ofsubstrates and a liquid crystal layer disposed therebetween, ischaracterized in that orientation control slope portions composed of anorganic film are provided on at least one of the substrates so as to beslopewise formed in different directions within each pixel, and anopaque shielding electrode is disposed at a boundary portion at whichthe slope direction is varied in each of the orientation control slopeportions.

According to a second aspect of the present invention, a liquid crystaldisplay device having a first substrate, a second substrate and a liquidcrystal layer disposed between the first substrate and the secondsubstrate, is characterized in that the first substrate comprises afirst transparent substrate, first transparent electrodes provided onthe first transparent substrate, orientation control slope portionswhich are slopewise formed in different directions within each pixel andcomposed of organic film and provided on the first transparentelectrodes and a first orientation layer coated on the orientationcontrol slope portions, the second substrate comprises a secondtransparent substrate, one or more second transparent electrodesprovided on the second transparent substrate and a second orientationlayer coated on the one or more second transparent electrodes, and anopaque shielding electrode is disposed a boundary portion at which theslope direction is varied in each of the orientation control slopeportions.

According to a third aspect of the present invention, a liquid crystaldisplay device having a first substrate, a second substrate and a liquidcrystal layer disposed between the first substrate and the secondsubstrate, is characterized in that the first substrate comprises afirst transparent substrate, pixel electrodes provided on the firsttransparent substrate, first orientation control slope portions whichare slopewise formed in different directions within each pixel andcomposed of organic film and provided on the pixel electrodes, and afirst orientation layer coated on the first orientation control slopeportions, the second substrate comprises a second transparent substrate,one or more opposite electrodes provided on the second transparentsubstrate, a second orientation control slope portions which areslopewise formed in different directions within each pixel and composedof organic film and provided on the one or more opposite electrodes, anda second orientation layer coated on the second orientation controlslope portions, the first and second orientation control slope portionsbeing formed so that the confronting surfaces thereof are substantiallyparallel to each other, and an opaque shielding electrode is disposed ata boundary portion at which the slope direction is varied in each of thefirst orientation control slope portions.

According to a fourth aspect of the present invention, a liquid crystaldisplay device having a first substrate, a second substrate and a liquidcrystal layer disposed between the first substrate and the secondsubstrate, is characterized in that the first substrate comprises afirst transparent substrate, pixel electrodes provided on the firsttransparent substrate, first orientation control slope portions whichare slopewise formed in different directions within each pixel andcomposed of organic film and provided on the pixel electrodes, and afirst orientation layer coated on the first orientation control slopeportions, the second substrate comprises a second transparent substrate,one or more opposite electrodes provided on the second transparentsubstrate, a second orientation control slope portions which areslopewise formed in different directions within each pixel and composedof organic film and provided on the one or more opposite electrodes, anda second orientation layer coated on the second orientation controlslope portions, the first and second orientation control slope portionsbeing formed so that the confronting surfaces thereof are substantiallyparallel to each other, and an opaque shielding electrode is disposed ata boundary portion at which the slope direction is varied in each of thesecond orientation control slope portions.

According to a fifth aspect of the present invention, a liquid crystaldisplay device having a pair of substrates and a liquid crystal layerdisposed therebetween, is characterized in that orientation controlslope portions composed of an organic film are provided on at least oneof the substrates so as to be slopewise formed in different directionswithin each pixel, the organic film being composed of organic materialcontaining no photosensitive group.

According to a sixth aspect of the present invention, a liquid crystaldisplay device having a first substrate, a second substrate and a liquidcrystal layer disposed between the first substrate and the secondsubstrate, is characterized in that the first substrate comprises afirst transparent substrate, first transparent electrodes provided onthe first transparent substrate, orientation control slope portionswhich are slopewise formed in different directions within each pixel andcomposed of organic film and provided on the first transparentelectrodes and a first orientation layer coated on the orientationcontrol slope portions, the second substrate comprises a secondtransparent substrate, one or more second transparent electrodesprovided on the second transparent substrate and a second orientationlayer coated on the one or more second transparent electrodes, theorganic film being composed of organic material containing nophotosensitive group.

According to a seventh aspect of the present invention, a liquid crystaldisplay device having a first substrate, a second substrate and a liquidcrystal layer disposed between the first substrate and the secondsubstrate, is characterized in that the first substrate comprises afirst transparent substrate, pixel electrodes provided on the firsttransparent substrate, first orientation control slope portions whichare slopewise formed in different directions within each pixel andcomposed of organic film and provided on the pixel electrodes, and afirst orientation layer coated on the first orientation control slopeportions, the second substrate comprises a second transparent substrate,one or more opposite electrodes provided on the second transparentsubstrate, a second orientation control slope portions which areslopewise formed in different directions within each pixel and composedof organic film and provided on the one or more opposite electrodes, anda second orientation layer coated on the second orientation controlslope portions, the first and second orientation control slope portionsbeing formed so that the confronting surfaces thereof are substantiallyparallel to each other, the organic film being composed of organicmaterial containing no photosensitive group.

The organic film constituting the orientation control slope portions ispreferably composed of material selected from the group consisting ofacrylic resin, polyimide, polysilazane, low-temperature curing typepolysilazane and benzocyclobutene.

According to a eighth aspect of the present invention, a method ofmanufacturing a liquid crystal display device comprising the steps of:

(1) coating an organic material on one or more electrodes of at leastone of a pair of substrates to form an organic film;

(2) coating photoresist on the organic film;

(3) exposing the photoresist to light;

(4) immersing the substrate in developing solution to performdevelopment and subjecting the organic film to wet etching with thedeveloping solution;

(5) exfoliating the photoresist;

(6) deforming the organic film by heating the organic film, andproviding on the substrate orientation control slope portions which aresloping in different directions respectively and formed of organic film;and

(7) coating an orientation film on the orientation control slopeportion.

The developing solution is preferably an alkali developing solution, andthe organic film is preferably composed of material that is dissolved inthe alkali developing solution.

According to a ninth aspect of the present invention, a method ofmanufacturing a liquid crystal display device comprising the steps of:

(1) coating an organic material on one or more electrodes of at leastone of a pair of substrates to form an organic film;

(2) coating photoresist on the organic film;

(3) exposing the photoresist to light;

(4) immersing the substrate in developing solution to performdevelopment;

(5) wet-etching the organic film;

(6) exfoliating the photoresist;

(7) deforming the organic film by heating the organic film, andproviding on the substrate orientation control slope portions which aresloping in different directions respectively and formed of organic film;and

(8) coating an orientation film on the orientation control slopeportions;

The developing solution is an alkali developing solution, and theorganic film is composed of material which is not dissolved in thealkali developing solution.

According to the liquid crystal display device of the present invention,the orientation control slope portions are formed so as to be slopewisein the different directions within each pixel, and thus the orientationstability of domains is enhanced. Further, since the orientation controlslope portion in each pixel is formed of the organic film, transparencyis very excellent.

According to the manufacturing method of the present invention, sincethe organic film which can be formed at a large thickness is subjectedto wet etching and then heated to form the orientation control slopeportions on the substrate, the orientation control slope portion whichis gently and widely sloping in different directions within each pixelcan be surely obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A is a cross-sectional view showing a pixel of a liquid crystaldisplay device according to a first embodiment of the present invention,and FIG. 1B is a diagram showing the direction of a rubbing treatmentwhich is conducted on orientation layers on a pixel substrate and aopposite substrate;

FIGS. 2A to 2F are cross-sectional views showing a series of steps of amanufacturing method of a liquid crystal display according to thepresent invention;

FIG. 3 is a cross-sectional view showing a liquid crystal display deviceaccording to a second embodiment of the present invention;

FIGS. 4A is a cross-sectional view showing a liquid crystal displaydevice according to a third embodiment of the present invention, andFIG. 4B is a diagram showing the direction of a rubbing treatment whichis conducted on orientation layers on a pixel substrate and a oppositesubstrate.

FIG. 5 is a cross-sectional view showing a liquid crystal display deviceaccording to a fourth embodiment of the present invention;

FIGS. 6A to 6F are cross-sectional views showing a series of steps of amanufacturing method of the liquid crystal display device of the fourthembodiment;

FIG. 7 is a cross-sectional view showing a liquid crystal display deviceaccording to a fifth embodiment of the present invention;

FIG. 8 is a diagram showing the operation of the liquid crystal displaydevice according to the first embodiment of the present invention;

FIG. 9 is a diagram showing the operation of the liquid crystal displaydevice according to the second embodiment of the present invention;

FIG. 10 is a perspective view showing a conventional liquid crystaldisplay device; and

FIGS. 11A to 11D are cross-sectional views showing a series of steps ofa method of manufacturing a substrate used in the conventional liquidcrystal display device.

FIG. 12 is an exploded perspective view showing the structure of theliquid crystal display device.

FIG. 13 is a plane view showing the structure of the pixel substrate.

FIG. 14 is an exploded perspective view showing a liquid crystal displaydevice according to a sixth embodiment of the present invention.

FIG. 15 is an exploded perspective view showing a liquid crystal displaydevice according to a seventh embodiment of the present invention.

FIG. 16 is an exploded perspective view showing a liquid crystal displaydevice according to a eighth embodiment of the present invention.

FIGS. 17, 18 are fragmentary exploded perspective views showing thepixel substrate and opposite substrate of the eighth embodiment.

FIG. 19 is an exploded perspective view showing the structure of theliquid crystal display device which two or more orientation controlslope portions are formed to within a pixel.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments according to the present invention will bedescribed hereunder with reference to the accompanying drawings.

FIG. 1A is a cross-sectional view showing a pixel of a liquid crystaldisplay device according to a first embodiment of the present invention.

As shown in FIG. 1A, the liquid crystal display device according to thefirst embodiment includes pixel substrate 1, opposite substrate 2 andliquid crystal layer 3 disposed between the pixel substrate 1 and theopposite substrate 2.

The pixel substrate 1 includes first transparent insulating substrate 4such as a glass substrate or the like, pixel electrodes 5 provided onthe first transparent insulating substrate 4, orientation control slopeportions 6 which are formed on the pixel electrodes 5 so as to be gentlysloping in a recess form in different directions within each pixel andcomposed of an organic film, and orientation layer 7 coated on theorientation control slope portions 6. The organic film constituting theorientation control slope portions 6 is formed of acrylic resin,polyimide, polyimide, polysilazane, low-temperature curing typepolysilazane or benzocyclobutene. The organic film is composed oforganic material containing no photosensitive group (such as naphthoquinone diazide, cinnamic acid).

The opposite substrate 2 has second transparent insulating substrate 8such as a glass substrate or the like, opposite electrode 9 provided onthe second transparent insulating substrate 8, and orientation layer 10coated on the opposite electrode 9.

The pixel electrodes 5 and the opposite electrode 9 are formed of atransparent conductive film such as ITO (Indium-Tin-Oxide) or the likeby a sputtering method or the like.

The orientation layer 7 of the pixel substrate 1 and the orientationlayer 10 of the opposite substrate 2 are formed of polyimide or thelike, and disposed so as to confront each other. Each of the orientationlayers 7 and 10 has such a characteristic that liquid crystal molecules11 are orientated substantially horizontally to the substrates 1, 2, andthe liquid crystal layer 3 contains liquid crystal having positivedielectric-constant anisotropy.

FIG. 1B is a diagram showing the direction of a rubbing treatment whichis conducted on the orientation layers 7 and 10 on the pixel substrate 1and the opposite substrate 2. As shown in FIG. 1B, the orientation layer7 of the pixel substrate 1 is subjected to the rubbing treatment in thedirection indicated by arrow 12, and the orientation layer 10 of theopposite substrate 2 is subjected to the rubbing treatment in thedirection indicated by arrow 13.

The pixel substrate 1 is provided with thin-film transistor (TFT) fordriving each pixel electrode 5. A plurality of pixels, each of which isformed between the pixel electrode 5 and the opposite electrode 9, arearranged in a matrix form.

FIG. 8 is a diagram showing the operation of the liquid crystal displaydevice according to the first embodiment.

As shown in FIG. 8, according to the property of the orientation layer7, the liquid crystal molecules 11 in the neighborhood of the interfacehave pretilt angle C to the interface. The slope angle of theorientation control slope portion 6 to the substrate 4 is angle B. Onthe other hand, the liquid crystal molecules 11 in the neighborhood ofthe orientation layer 10 has pretilt angle A. Giving such orientationcontrol force, the angle of the liquid crystal molecules 11 to thesubstrate 4 in the neighborhood of the orientation layer 7 is equal to(B−C) in area α and (B+C) in area β. If (B+C) or (B−C) is larger than A,the liquid crystal molecules are oriented to rise up in a directionwhich is determined by the angle of (B+C) or (B−C) when driving electricfield 14 is applied in the direction vertical to the substrate.

For example, when angle A, B and C are equal to 1 degree, 5 degrees and1 degree respectively, the liquid crystal molecules rise up clockwisewith respect to the substrate in the area α and counterclockwise withrespect to the substrate in the area β.

When the pretilt angles A and B are small, the liquid crystal moleculesin area α′ having no slope which is adjacent to the area α and theliquid crystal molecules in areaβ′ having no slope which is adjacent tothe area β rise up in the same rise-up directions of the areas α and β,respectively.

If the liquid crystal orientation direction (rise-up direction) isdifferent between the areas α and β, the viewing angle characteristicwhen a viewpoint is inclined is compensated (enhanced) by the respectiveareas in each pixel, whereby a wide visual field can be obtained.

Through the above operation, domains having different rise-up directionswith each pixel are formed, and a liquid crystal display device having awide rage of viewing angle can be obtained.

According to the liquid crystal display device of this embodiment, theorientation control slope portion 6 is gently slopewise formed indifferent directions within each pixel, so that the orientationstability of domains is enhanced.

Further, the orientation control slope portion 6 is formed of an organicfilm, so that the transparency of the device is excellent and a displayimage can be prevented from being darkened or colored.

The orientation control slope portion 6 of the pixel substrate 1 may beformed in a convex form.

FIGS. 2A to 2F is a cross-sectional view showing a method ofmanufacturing the liquid crystal display device of the presentinvention.

First, the pixel electrode 5 (transparent electrode) of ITO or the likeis formed on the first transparent insulating substrate 4 by thesputtering method. Subsequently, organic film material (for example,acrylic resin) diluted with organic solvent is coated on the pixelelectrode 5 by a spin coating method so as to obtain a film thickness of3 μm. Thereafter, the organic film material on the substrate is heatedand temporarily burned for 1 minute on a hot plate at 100° C. to formthe organic film 16.

Subsequently, the photoresist 17 is formed on the organic film 16 by thespin coating method, and heated for 1 minute on the hot plate of 80° C.to temporarily burn the photoresist 17 (see FIG. 2A).

Subsequently, light having energy of about 100 mJ/cm² is irradiated tothe photoresist 17 by a stepper to thereby perform an exposure step (seeFIG. 2B).

Next, the first transparent insulating substrate 4 is immersed in alkalideveloping solution (containing 2.38% of TMAH (tetramethylammoniumoxide)) for 140 seconds to perform development. The photoresist 17 usedin this step is a positive type resist, and thus a portion of thephotoresist to which the light is irradiated is dissolved in thedeveloping solution at a developing step which is the next step. Theorganic film 16 used in this step has such a property that it isdissolved in the alkali developing solution when it is burned at about100° C., and thus the organic film 16 is subjected to a wet etchingtreatment simultaneously with the developing treatment (see FIG. 2C).Since the wet etching treatment is an isotropic etching treatment, aslope face is formed on the etched surface. Therefore, a continuousorientation control slope portion 6 can be formed over a wide range whenthe orientation control slope portion 6 is formed in a subsequent step,and the orientation direction of the liquid crystal molecules can beeffectively controlled.

Subsequently, after the development treatment, post-bake is carried outon the hot plate of 130° C. This step is performed to promote a crosslinking reaction of the organic film 16 and enhance the resistance ofthe organic film 16 to dissolution in an exfoliating liquid in asubsequent resist exfoliating step. Thereafter, light having an energydensity of 300 mJ/cm² is exposed to the whole surface of the substrate.This step is performed to reduce the resistance of the photoresist 17 toexfoliation in the subsequent resist exfoliation step.

Subsequently, the photoresist 17 is exfoliated by immersing thesubstrate in the exfoliating liquid for 90 seconds (see FIG. 2D).

Subsequently, when the substrate is heated under an atmosphere of ahigher temperature than the glass transition point of the organic film16 (200° C.), for example, at 300° C. for 30 minutes by an oven, theshape of the organic film 16 is varied, and a gentle slope surface isformed, whereby orientation control slope portion 6 is formed (see FIG.2E). By suitably selecting the film forming condition of the organicfilm 16 and the etching condition, a sufficiently continuous slopesurface can be formed over a wide area within about 100 μm from theetching edge. Accordingly, since the pixel size of the normal liquidcrystal display device is equal to 200 to 350 μm, most of pixels can besloped by forming an etching portion in each pixel.

Subsequently, polyimide or the like is coated on the orientation controlslope portion 6 and burned to form the orientation layer 7, therebyforming the pixel substrate 1 (see FIG. 2F).

The opposite electrode 9 of ITO or the like is formed on the secondtransparent insulating substrate 8 as in the case of the pixel substrate1, and then the orientation layer 10 is formed on the opposite electrode9 to form the opposite substrate 2.

Subsequently, the orientation layer 7 of the pixel substrate 1 issubjected to the rubbing treatment in the direction indicated by thearrow 12 in FIG. 1B, and the orientation layer 10 of the oppositesubstrate 2 is subjected to the rubbing treatment in the directionindicated by the arrow 13 in FIG. 1B.

Subsequently, the pixel substrate 1 and the opposite substrate 2 aresuperposed, and then nematic liquid crystal having positivedielectric-constant anisotropy is injected into the gap between thesubstrates.

Subsequently, the pixel substrate 1 and the opposite substrate 2 thussuperposed are sandwiched by two polarizers whose polarization axes arecrossed to each other by 90 degrees and respectively intersect to therubbing direction at an angle of 45 degrees as indicated by arrows 18 inFIG. 1B.

According to the manufacturing method of the present invention, theorganic film 16 which can be designed to have a large thickness issubjected to the wet etching treatment, and then heated to form theorientation control slope portion 6. Therefore, the orientation controlslope portion 6 which is gently and widely sloped in differentdirections within each pixel can be surely achieved.

In the above manufacturing method, the development of the photoresist 17and the wet-etching treatment of the organic film 16 can besimultaneously performed. However, when material which is not dissolvedin alkali developing solution (for example, polyimide, polysilazane,low-temperature curing type polysilazane or benzocyclobutene) is usedfor the organic film 16, the development of the photoresist 16 and thewet-etching treatment of the organic film 16 may be separatelyperformed.

When polysilazane or low-temperature curing type polysilazane is used asthe material of the organic film 16, as compared with general organicmaterials, the thermal shrinkage is smaller and a more close insulatingfilm can be achieved. As a result, crack due to shrinkage stress at thefilm formation time does not occur, and a close film can be obtained, sothat there can be provided a liquid crystal display device whichdecreases display defective due to impurities and thus provides highimage quality.

FIG. 12 is an exploded perspective view showing the structure of theliquid crystal display device. As shown FIG. 12, orientation controlslope portion 6 of the pixel substrate 1 is formed to extend over twopixel electrodes 5, and two orientation control slope portions 6 arepartially disposed on pixel electrode 5 of each pixel.

Consequently, the two orientation control slope portions 6 make up aconcave form in each pixel so as to be gently sloping in differentdirections in each pixel. The pixel substrate 1 and the oppositesubstrate 2 are sandwiched between polarizers 70 and 73. The oppositeelectrode 9 is a common electrode faced to all pixel electrodes 5.

FIG. 13 is a plane view showing the structure of the pixel substrate 1.As shown FIG. 13, pixel electrode 5 and TFT 77 are formed within apixel. The pixel electrode 5 in each pixel is connected with signalelectrode line 78 through TFT 77. The gate of TFT 77 is connected withscanning electrode line 79.

In FIG. 12, TFT 77, signal electrode line 78 and scanning electrode line79 are omitted.

As shown FIG. 19, two orientation control slope portions 6 may be formedto within a pixel. In FIG. 19, TFT 77, signal electrode line 78,scanning electrode line 79 and pixel electrode 5 are omitted. More thantwo orientation control slope portions 6 may be formed to within apixel.

FIG. 3 is a cross-sectional view showing a liquid crystal display deviceaccording to a second embodiment of the present invention.

In the second embodiment, the orientation layer 7 has such a propertythat the liquid crystal molecules 11 are oriented substantiallyvertically to the substrate 4, and the liquid crystal of the liquidcrystal layer 3 has negative dielectric-constant anisotropy. The otherstructure of the pixel substrate 1 and the opposite substrate 2 and themanufacturing method are similar to those of the first embodiment.

The pixel substrate 1 and the opposite substrate 2 are sandwichedbetween two polarizers whose polarization axes are crossed to each otherby 90 degrees so as to intersect to the inclination direction of theliquid crystal molecules 11 by 45 degrees

FIG. 9 is a diagram showing the operation of the liquid crystal displaydevice according to the second embodiment of the present invention.

In FIG. 9, according to the property of the orientation layer 7, theliquid crystal molecules 11 in the neighborhood of the interface areinclined to the interface by 90 degrees. Here, the inclination angle ofthe orientation control slope portion 6 to the substrate 4 is set toangle B. Giving these orientation control force, the inclination angleof the liquid crystal molecules 11 to the substrate 4 in neighborhood ofthe pixel substrate 1 is equal to (90+B) in an area α and (90−B) in anarea β. Since the dielectric-constant anisotropy of the liquid crystalis negative, the liquid crystal molecules 11 is inclined in a directionwhich is regulated by the angle (90+B) or (90−B) when a voltage isapplied. As a result, areas having different liquid crystal orientationdirections (inclination directions) occur in each pixel, and the viewingangle characteristic when the viewpoint is inclined is compensatedbetween the respective areas in each pixel, thereby obtaining a widevisual field characteristic.

According to the second embodiment, the inclination direction of theliquid crystal is regulated by the orientation control slope portion 6,so that no rubbing treatment is necessary and thus the number of themanufacturing steps can be reduced.

FIG. 4A is a cross-sectional view showing a liquid crystal displaydevice according to a third embodiment of the present invention, andFIG. 4B is a diagram showing the direction of the rubbing treatment tobe subjected to the orientation layers 7, 10 on the pixel substrate 1and opposite substrate 2.

In the third embodiment, an opaque shielding electrode 20 is disposed ona first transparent insulating substrate 4 at a portion where theorientation direction (rise-up direction) of the liquid crystalmolecules 11 is varied. Further, the pixel electrode 5 is provided onthe shielding electrode 20 so as to be electrically connected to theshielding electrode 20. The other structure of the pixel substrate 1,the opposite substrate 2 and the liquid crystal layer 3 and themanufacturing method are similar to the first embodiment.

In general, in the liquid crystal molecules 11, defective (hereinafterreferred to as “dislocation”) occurs at a portion where the molecularorientation is discontinuously changed, and it is observed as lightleakage at a black display time. When such dislocation occurs, thecontrast is reduced and thus no high-quality display is obtained.

However, according to the third embodiment, the portion at which thedislocation occurs and the rise-up direction is varied (represented by Tin FIG. 4A) can be shielded by the opaque shielding electrode 20, sothat the contrast is not reduced and thus higher image quality can beobtained.

FIG. 5 is a cross-sectional view showing a liquid crystal display deviceaccording to a fourth embodiment of the present invention.

In the fourth embodiment, an orientation control slope portion 30 isprovided on the opposite electrode 9 of the opposite substrate 2. Theslope surface of the orientation control slope portion 30 of theopposite substrate 2 is formed to be substantially parallel to the slopesurface of the orientation control slope portion 6 of the pixelsubstrate 1. That is, the orientation control slope portion 6 of thepixel substrate 1 is formed in a recess (concave) form, and theorientation control slope portion 30 of the opposite substrate 2 isformed in a convex form. The orientation control slope portion 6 of thepixel substrate 1 may be formed in a convex form while the orientationcontrol slope portion 30 of the opposite substrate 2 is formed in aconcave form. The orientation layer 10 is provided on the orientationcontrol slope portion 30 of the opposite substrate 2.

The pixel substrate 1 and the opposite substrate 2 are disposed so thatthe orientation layers 7 and 10 are confronted to each other, and theliquid crystal layer 3 is disposed between the orientation layers 7 and10.

The orientation layers 7, 10 used in the fourth embodiment have such aproperty that the liquid crystal molecules 11 are oriented substantiallyparallel to the substrate, and the liquid crystal of the liquid crystallayer 3 has positive dielectric-constant anisotropy.

The pixel substrate 1 and the opposite substrate 2 are sandwiched by twopolarizers whose polarization axes are crossed to each other by 90degrees so as to intersect to the inclination direction of the liquidcrystal molecules 11 at an angle of 45 degrees.

FIGS. 6A to 6F are cross-sectional views showing a method ofmanufacturing the liquid crystal display device according to the fourthembodiment of the present invention. FIG. 2 shows the method ofmanufacturing the pixel substrate on which the orientation control slopeportion 6 is designed in a concave shape, however, FIG. 6 shows themethod of manufacturing the opposite substrate 2 on which theorientation control slope portion 30 is designed in a convex shape. Thevarious conditions such as temperature are the same as the manufacturingmethod shown in FIG. 2.

First, the opposite electrode 9 (transparent electrode) such as ITO orthe like is formed on the second transparent insulating substrate 8 bythe sputtering method.

Subsequently, organic film material (for example, acrylic resin) dilutedwith organic solvent is coated on the opposite electrode 9 by the spincoating method. Thereafter, it is heated and temporarily burned on a hotplate to form the organic film 16.

Subsequently, the photoresist 17 is formed on the organic film 16 by thespin coating method, and heated and temporarily burned on the hot plate(see FIG. 6A).

Subsequently, light is irradiated to the photoresist 17 by using astepper to complete an exposure step (see FIG. 6B). At this time, boththe end portions of each pixel are exposed to light.

Subsequently, the second transparent insulating substrate 8 is immersedin alkali developing solution to be developed. Since the photoresist 17used in this step is positive type resist, a part of the resist which isexposed to light will be dissolved in the developing solution in thesubsequent developing step. The organic film 16 used in this step isinherently dissolved in the alkali developing solution, and thus thewet-etching treatment of the organic film 16 is carried outsimultaneously with the developing step (see FIG. 6C). The wet-etchingtreatment is an isotropic etching treatment, and thus a slope face isformed on the etched surface. Therefore, a continuous orientationcontrol slope portion 30 can be formed in a wide range when theorientation control slope portion 30 is formed in the subsequent step,so that the orientation direction of the liquid crystal can beeffectively controlled.

Subsequently, after the developing treatment, the post-bake treatment iscarried out on the hot plate. This step is carried out to promote thecross linking reaction and enhance the resistance of the organic film 16to dissolution in the exfoliating liquid in the subsequent resistexfoliating step. Thereafter, the whole surface of the substrate isexposed to light. This step is carried out to reduce the resistance ofthe photoresist 17 to exfoliation in the subsequent resist exfoliatingstep.

Subsequently, the photoresist 17 is exfoliated by immersing it into theexfoliating liquid (see FIG. 6D).

Subsequently, upon heating by an oven, the organic film 16 is deformed,and the orientation control slope portion 30 having a gentle slopesurface is formed (see FIG. 6E). A sufficiently continuous slope surfacecan be formed by suitably selecting a film forming condition of theorganic film 16 and an etching condition.

Thereafter, polyimide or the like is coated on the orientation controlslope portion 30 and burned to form the orientation layer 10, therebyobtaining the opposite substrate 2 (see FIG. 6F).

FIG. 7 is a cross-sectional view showing a liquid crystal display deviceaccording to a fifth embodiment of the present invention.

In the fifth embodiment, the orientation layer 7 has such a propertythat the liquid crystal molecules 11 are oriented substantiallyvertically to the substrate, and the liquid crystal of the liquidcrystal layer 3 has negative dielectric-constant anisotropy. The otherstructure of the pixel substrate 1 and the opposite substrate 2 and themanufacturing method are similar to the fourth embodiment.

The pixel substrate 1 and the opposite substrate 2 are sandwiched by twopolarizers whose polarization axes are crossed to each other by 90degrees so as to intersect to the inclination direction of the liquidcrystal molecules 11 by 45 degrees.

According to the fourth and fifth embodiments, the orientation controlslope portion 30 is provided to not only the pixel substrate 1, but alsothe opposite substrate 2, and the pixel substrate 1 and the oppositesubstrate 2 are disposed so that the confronting surfaces of theorientation control slope portions 6 and 30 thereof are parallel to eachother. Therefore, the tilt angle of the liquid crystal in the bulk ofthe liquid crystal layer 3 can be stabilized. As a result, the rise-updirection of the liquid crystal is stabilized, and the orientationstability of the domains is enhanced.

FIG. 14 is an exploded perspective view showing a liquid crystal displaydevice according to a sixth embodiment of the present invention. Asshown FIG. 14, one orientation control slope portion 6 is formed tocover one pixel electrode 5 in each pixel. Consequently, the orientationcontrol slope portion 6 makes up a convex form in each pixel so as to begently sloping in different directions in each pixel. In FIG. 14, theorientation control slope portion 6 covers only pixel electrode 5. Theorientation control slope portion 6 may cover the pixel electrode 5 andTFT 77 or the whole of a pixel.

FIG. 15 is an exploded perspective view showing a liquid crystal displaydevice according to a seventh embodiment of the present invention. Asshown FIG. 15, the orientation control slope portion 6 of thisembodiment is arranged to turn the orientation control slope portion 6of FIG. 14 at 90°. The slope of the orientation control slope portion 6may be arranged in any direction.

The above embodiments of the present invention are used for the liquidcrystal display device of the TFT form. This invention may be applied tothe liquid crystal display device of simple matrix form in which liquidcrystal such as STN (Super Twisted Nematic) is used.

The following will explain about the embodiment.

FIG. 16 is an exploded perspective view showing a liquid crystal displaydevice according to a eighth embodiment of the present invention. InFIG. 16, the orientation control slope portions 6 are omitted.

FIGS. 17 and 18 are fragmentary exploded perspective views showing thepixel substrate and opposite substrate of the eighth embodiment. Thestructure of FIG. 17 corresponds to the first embodiment of FIG. 12, andthe structure of FIG. 18 corresponds to the sixth embodiment of FIG. 14.In FIG. 17, orientation control slope portions 86 is formed to extendover two pixel electrodes 84. In FIG. 18, orientation control slopeportion 86 is formed to cover a width direction part of pixel electrode5.

As shown FIG. 16, the pixel substrate 81 and the opposite substrate 82are sandwiched between polarizers 80 and 83. As shown FIG. 16, pixelelectrodes 84 and opposite electrodes 85 are respectively composed ofthe electrodes arranged in parallel, and the part where one line ofpixel electrodes 84 and one line of opposite electrodes 85 cross eachother becomes a pixel.

The present invention is not limited to the above embodiments, andvarious modifications may be made without departing from the subjectmatter of the present invention.

According to the liquid crystal display device of the present invention,the orientation control slope portion is gently slopewise formed indifferent directions within each pixel, so that the orientationstability of the domains is enhanced.

Further, the orientation control slope portion is formed of an organicfilm, so that the transparency is enhanced and the display image can beprevented from being darkened or colored.

According to the manufacturing method of the present invention, theorganic film which can be designed to have a large thickness iswet-etched and then heated to form the orientation control slopeportion. Therefore, the orientation control slope portion that is gentlyand widely sloped in different directions within each pixel can besurely achieved.

What is claimed is:
 1. A liquid crystal display device having a firstsubstrate, a second substrate and a liquid crystal layer disposedbetween the first substrate and the second substrate, wherein said firstsubstrate comprises a first transparent substrate, pixel electrodesprovided on said first transparent substrate, first transparentorientation control slope portions which are slopewise formed indifferent directions within each pixel and composed of an organic filmand provided on said pixel electrodes, and a first orientation layercoated on the first transparent orientation control slope portions, saidsecond substrate comprises a second transparent substrate, one or moreopposite electrodes provided on said second transparent substrate,second transparent orientation control slope portions which areslopewise formed in different directions within each pixel and composedof an organic film and provided on said one or more opposite electrodes,and a second orientation layer coated on said second transparentorientation control slope portions, said first and second transparentorientation control slope portions being formed so that the confrontingsurfaces thereof are substantially parallel to each other, said organicfilm being composed of organic material containing no photosensitivegroup.
 2. The liquid crystal display device as claimed in claim 1,wherein said organic film constituting said first and second orientationcontrol slope portions are composed of material selected from the groupconsisting of acrylic resin, polyimide, polysilazane, low-temperaturecuring type polysilazane and benzocyclobutene.
 3. The liquid crystaldisplay device as claimed in claim 1, wherein said liquid crystal layercomprises a plurality of liquid crystal molecules that are orientedsubstantially vertically with respect to the first and secondsubstrates.
 4. The liquid crystal display device as claimed in claim 1,wherein said liquid crystal layer has a negative dielectric-constantanisotropy.
 5. The liquid crystal display device as claimed in claim 1,wherein each of said first and second transparent orientation controlslope portions is disposed so as to cover only a portion of twoadjacently positioned ones of said pixel electrodes.